Such a pressure measuring transducer comprises a measuring membrane and a circuit for transducing a pressure dependent deformation of the measuring membrane to an electrical signal. The circuit can comprise, for example, a (piezo-) resistive bridge circuit or a capacitive circuit having at least two electrodes, wherein the measuring membrane has at least one resistor of the bridge circuit or one of the electrodes. In process measurements technology, a semiconductor pressure measuring transducer is usually supplied with a process pressure to be measured via a pressure transfer means, since available semiconductor materials are scarcely able directly to withstand the varied media and process conditions of the process industry. A pressure transfer means comprises a hydraulic path, which extends through a solid body, usually of metal, between a first opening and a second opening; wherein the first opening is sealed by an isolating diaphragm, which is contactable with a pressure to be measured, in order to introduce the pressure to be measured into the hydraulic path; wherein the hydraulic path opens into a transducer chamber at the second opening. The pressure measuring transducer is arranged in the transducer chamber. The transducer chamber is sealed by the measuring membrane of the pressure measuring transducer. The hydraulic path contains a transfer liquid for the transfer of pressure. This transfer liquid has a coefficient of thermal expansion that is significantly greater than the coefficient of thermal expansion of the surrounding solid body. This causes temperature dependent deflections of the isolating diaphragm and brings about a corruption of the pressure introduced into the hydraulic path due to the not insignificant stiffness of the isolating diaphragm. Consequently it is advantageous to minimize the volume of the hydraulic path and, respectively, the transfer liquid, for which purpose, for example, filling elements are brought into the transducer chamber, in order to fill manufacturing related hollow spaces between the metal walls of the transducer chamber and the semiconductor pressure measuring transducer. Especially when manufactured of plastic in the form of injection molded parts, the filling elements can be fitted as accurately as desired to the contours of the hollow spaces to be filled. A pressure sensor with such a filling element for filling the hollow space between the cylindrical lateral surface of a transducer chamber wall and the semiconductor transducer is sold by the assignee under the name Cerabar M.
Insofar as the transducer chamber is formed in a metal material, Cerabar M additionally has an insulator plate made of synthetic material arranged in the transducer chamber. The insulator plate is biased against the filling element by a spring, which is supported on an end of the transducer chamber wall, in order, on the one hand, to insulate the measuring membrane from the metal wall and, on the other hand, to hold the filling element and the insulator plate in position.
Assembly of the filling element, the insulator plate, and the spring requires a large manual effort. Additionally, the volume taken up by the spring and required for the working stroke of the spring cannot be directly limited with a filling element. Thus, there are limits here as to how much the volume of the transfer liquid can be minimized.